The method for producing methyl methacrylate by means of a gas-phase catalytic reaction using methyl α-hydroxyisobutyrate as a raw material is publicly known. For example, Patent Document 1 discloses a method for producing an α,β-unsaturated carboxylic acid ester in which α-hydroxycarboxylic acid ester, α-alkoxycarboxylic acid ester and β-alkoxycarboxylic acid ester are used solely or in combination as a raw material to carry out a dehydration or dealcoholization reaction with a crystalline alumino silicate as a catalyst. Regarding the crystalline alumino silicate to be used in the production method, the document describes that X-type or Y-type zeolite exhibits particularly excellent catalytic activity. Further, Patent Documents 2, 3 and 4 disclose that a crystalline alumino silicate modified with an alkali metal and/or a platinum group element, in particular, X-type or Y-type zeolite is effective as a catalyst for the production method.
In the case of producing methyl methacrylate from methyl α-hydroxyisobutyrate by means of a gas-phase catalytic reaction using such a crystalline alumino silicate as a catalyst, it is known that there are problems such as temporal deterioration of the catalyst, which is caused because a high boiling point byproduct covers pore inlets of the crystalline alumino silicate, and coloring of a reaction solution due to by-produced diacetyl.
Regarding these problems, Patent Document 5 discloses that when a transition-type synthetic faujasite-type zeolite having a lattice constant in the boundary region between X type and Y type and a defined Na content is used, the production of diacetyl that is a coloring substance can be suppressed, and at the same time, the by-production of the high boiling point byproduct can be reduced to maintain the catalytic activity for a long period of time. In this regard, the document describes that a clay having an aluminium content of less than 5 wt %, in particular, a silica magnesia-based clay is preferably used as a binder for suppressing the by-production of diacetyl.
In addition, Patent Document 6 discloses that when using a catalyst containing, as an active component, a synthetic faujasite-type zeolite with the amount of free alkali being adjusted to 0.1 milliequivalent/g or less, or a molded catalyst obtained by using a synthetic faujasite-type zeolite and a clay whose pH is less than 9 when it is dispersed in water, the by-production of a high boiling point byproduct that causes temporal deterioration of the catalyst is suppressed, and the catalyst life becomes longer.